Trisomy greatly enhances interstitial crossing over in a translocation heterozygote of Secale

Abstract

Chromosomal rearrangements, including reciprocal translocations, may prevent recombinational transfer of genes from a donor genotype to a recipient, especially when the gene is located in an interstitial segment. The effect of trisomy of chromosome arm 1RS on recombination was studied in translocation heterozygote T248W of rye ( Secale cereale ), involving chromosome arms 1RS and 6RS. (Pro)metaphase I configuration frequencies were analyzed. Crossing over, estimated as chiasma parameters, in five genetically different euploid heterozygotes was compared with those of 10 different single arm trisomics. The addition of 1RS greatly altered the crossing over pattern around the translocation break point, with a special increase in the interstitial segment of 6RS and adjoining regions, normally hardly accessible to recombination. Furthermore, there was considerable variation between plants of closely related genotypes. Heterogeneity widens the distribution of crossing overs, including segments normally not accessible to recombination, but decreases average recombination in other segments. The extra chromosome and abnormal segregants are eliminated by using the trisomic as the pollen parent.

Induced Reciprocal Translocation in <i>Pisum sativum</i> L.

“…Almost all the PMCs observed showed the presence of interchange complexes except in PT 5 where some PMCs showed the presence of 7 bivalents too. The number of ring quadrivalents was more than that of chain quadrivalents in 3 translocation heterozygotes (PT 1 , PT 2 , and PT 4 ) suggesting that the interchanged segments are quite long and chiasma are formed among all the 4 chromosomes (Verma and Raina, 1990, Wijnker and de Jong, 2008, Sybenga et al 2012.…”

“…Translocation heterozygotes are characterized by the occurrence of new morphological chromosomal units out of segments of non-homologous chromosomes. Recently, Sybenga et al (2012) have found that trisomy greatly enhances interstitial crossing-over in a translocation heterozygote of Secale.The aim of the present study was to induce translocation and if possible produce a genetic map of the P. sativum, as has been done for Vicia faba (Rieger and Michaelis 1962, Schubert et al 1982, 1991. Karyotype reconstruction either natural or induced is of great importance to plant breeders and geneticists (Schubert et al 1991).…”

Can epigenetic control explain pronounced within-plant heterogeneity of meiosis in a translocation trisome ofSecaleL.?

“…The analysis was suspended when heterogeneity between closely related plants and even within plants made any valid conclusion impossible. Later, Sybenga et al (2012) recovered part of the old scoring lists and analyzed a small part to study the effect of the extra chromosome arm on recombination in the interstitial segments of the translocation. Within plant heterogeneity was not considered, which is the main topic of the present report.…”

“…Both types had been backcrossed for at least six generations to a series of inbred lines, and a series of hybrids of genetically different but specific combinations resulted. Sister plants from the same cross, supposed to be closely related and grown under identical conditions, appeared to be very different in meiotic behaviour (Sybenga et al 2012). Part of the variation can be the result of the relative ineffectiveness of backcrossing translocations and trisomics, but this was considered an insufficient explanation for the striking differences There are two types of material.…”

“…Of all tillers, the frequencies of 17 different metaphase I configurations were scored in 250 cells per tiller. The characteristics and origin of such configurations are described by Sybenga (1975) and Sybenga et al (2012). (ii) Thirteen plants of which four to seven tillers per plant were studied, grown both at 15°C and 20°C.…”